99 ds. Fe290 no start

[Bansheetaz]

Wont consistently start. If i feather the throttle back it will start and maybe catch and run fine. Push throttle too far and it will just crank with small pops from the intake like a lean condition. If it does start and run it will run great. Spark plug appears dry when i check it. Seems to pump plenty of fuel.
Things i have checked or replaced are as follows

Carb is new.
Fuel pump is new
Spark plug is new
Coil and rev limiter are new last fall
New fuel lines and filters
Valves set to .005
175 psi compression
Intake gaskets are new
Never looses spark which is nice and blue

I have found many other threads on the internet of folks with the same issue but no solutions. I used to be able to just mash the gas and it would take off. Now its intermittent as to whether it starts. Driving me bonkers.

Thank you for any ideas

[CP241]

Remove the cover to the black electrical box next to the motor. Turn the key OFF. Then slowly press on the gas pedal. Watch the carb and listen for the microswitches in the black box to click. I’ll bet the carb starts to open before or at the same time the microswitches click.

You can use the cable going into the black box and loosen it some, so the microswitches click, then the carb should NOT move until you press the gas pedal another inch down or so before it starts to open.

Also make sure the carb closes all the way when you release the gas. If the cable running from the governor to the carb gets sticky, it can hold it open and make it hard to start.

[kantuckian]

Thanks for Posting

[Bansheetaz]

I will check all that thank you

[Bansheetaz]

Originally Posted by CP241

Remove the cover to the black electrical box next to the motor. Turn the key OFF. Then slowly press on the gas pedal. Watch the carb and listen for the microswitches in the black box to click. I’ll bet the carb starts to open before or at the same time the microswitches click.

You can use the cable going into the black box and loosen it some, so the microswitches click, then the carb should NOT move until you press the gas pedal another inch down or so before it starts to open.

Also make sure the carb closes all the way when you release the gas. If the cable running from the governor to the carb gets sticky, it can hold it open and make it hard to start.

That all looks good. Im leaning towards an exhaust valve not sealing very well when the engine is warm creating an EGR effect. Maybe even partially burned. Im going to do a leak down and probably pull the head and see how it seals

[Fairtax4me]

New carb chinese?

Did you adjust the throttle plate or the idle mixture screw?
Remove the idle mixture pilot jet, the brass screw that sticks straight up out of the front side of the carb, and see if they overtightened the snot out of it and crushed the pilot holes in the screw. If they did it will never start right unless you replace the screw.

[crash12888]

The scenario described above regarding throttle adjustment is more for blatant backfiring from coasting and taking off again.

Tell us how it reacts when you go to start it with a little bit of choke?
I agree with Fairtax, sounds like a lean condition in the low speed circuit of the carb.
A little bit of choke will tell you if that is the case, then need to determine how to correct it, I have had brand new carbs out of box with milling shavings in them.
I also would lean toward going back with the original carb after you clean and blow it out.
Spray carb cleaner will not dissolve aged varnish, you need to get the gallon can of "Gunk" brand or equivalent carb cleaner and tear it completely down and soak it for at least an hour, then rinse with water then blow out with air.
Rinse with water first because you don't want to blow the carb cleaner on anything else.

[Bansheetaz]

Ive had 2 carbs on it and both have been disassembled and cleaned as i was checking for water and dirt contamination on both.one original and one new chinese carb. It will run on both perfectly sometimes. But They both act exactly the same with this problem. Sometimes it will start and run perfectly and othe times it will just crank. I no longer feel this is a fuel delivery problem. 2 different carbs, fuel pumps, new lines and filters. Always the same problem. A shot of ether will wake it up when its having an episode. Im leaning towards a valve problem or maybe a weird head gasket problem. 175psi compression when tested. I will do leakdown qhen i get a chance. This is very strange.